A chemical liquid valve for controlling a chemical liquid for a semiconductor manufacturing apparatus heretofore uses such a diaphragm valve as shown in FIG. 3, for example. This diaphragm valve 100 has a body 110 formed therein with a first flow passage 111 and a second flow passage 112 which have lateral ports and open in an upper surface of the body 110. The second flow passage 112 communicates with a valve port 114 formed in a valve seat 113. The first flow passage 111 communicates with a region surrounding the valve seat 113. On the upper surface of the body 110 in which one end of each of the first flow passage 111 and the second flow passage 112 opens, a diaphragm valve element 115 is placed. A peripheral portion of the diaphragm valve element 115 is anchored to define an airtight space around the openings of the first and second flow passages 111 and 112.
The diaphragm valve element 115 includes a valve element body 117 which can come into or out of contact with the valve seat 113 and a web (or diaphragm) portion 118 extending from a side surface of the valve element body 117. An annular fixed portion 119 formed at a peripheral edge of the web portion 118 is anchored between the body 110 and a cylinder 120. In the cylinder 120, a piston rod 121 is placed slidably in a vertical direction and is coupled at its lower end to the valve element body 117 of the diaphragm valve element 115. A cover 122 is attached to an upper portion of the cylinder 120, and a spring 123 is mounted in the cover 122 to urge the piston rod 121 downward. The cylinder 120 is further formed with an operation port 125 through which air is supplied to pressurize the piston rod 121 against the urging force of the spring 123.
In this diaphragm valve 100, therefore, the piston rod 121 is constantly urged downward by the spring 123, thereby pressing the valve element body 117 of the diaphragm valve element 115 against the valve seat 113 to close the valve. As compressed air is supplied through the operation port 125 of the cylinder l20, the piston rod 121 is pressurized from below to move upward against the urging force of the spring 123. Accordingly, the valve element body 117 coupled to the lower end of the piston rod 121 is also moved upward away from the valve seat 113, permitting communication between the first path 111 and the second path 112, so that the valve is placed in an open state. When the supplied compressed air is discharged through the operation port 125, the piston rod 121 urged by the spring 123 is moved downward, and the valve is returned to a closed state again as shown in the figure.
However, the above diaphragm valve has a problem in durability because, when the diaphragm is bent, stress may concentrate on the web portion of the diaphragm, especially, a root portion of the web portion continuous with the valve element body. In other words, a boundary portion between the web portion and the valve element body tends to be deteriorated, which is problematic. To avoid such a problem, various measures for the diaphragm valve have been taken to prevent the stress concentration on the web portion of the diaphragm, especially, the root portion of the web portion continuous with the valve element body.
As one of the diaphragm valves having adopted such measures, for example, there is a diaphragm valve disclosed in JP-A-9-217845. This disclosed diaphragm valve comprises a diaphragm including a central valve element, an annular thin web portion integrally formed around the valve element, and a cylindrical holding part integrally formed around the annular thin web portion. The annular thin web portion is formed in an upwardly curved shape in section with an inner peripheral root portion nearly vertically continuous with an upper surface of the valve element and an outer peripheral root portion nearly vertically continuous with an upper edge of an inner surface of the cylindrical holding part.
During valve opening/closing operations, the above configuration of the diaphragm valve permits only the curved portion of the annular thin web portion to be elastically deformed and keeps the inner and outer root portions in a nearly vertical form to prevent the inner and outer root portions from becoming subject to the bending stress, thus achieving improved durability of the diaphragm.
[Patent Document 1] JP-A-9-217845